Support "shared" histograms between processes.

base/metrics/sample_vector.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // SampleVector implements HistogramSamples interface. It is used by all
 // Histogram based classes to store samples.
 
 #ifndef BASE_METRICS_SAMPLE_VECTOR_H_
 #define BASE_METRICS_SAMPLE_VECTOR_H_
 
@@ skipping 32 matching lines @@
 
  protected:
   bool AddSubtractImpl(
       SampleCountIterator* iter,
       HistogramSamples::Operator op) override;  // |op| is ADD or SUBTRACT.
 
   virtual size_t GetBucketIndex(HistogramBase::Sample value) const;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptSampleCounts);
+  FRIEND_TEST_ALL_PREFIXES(SharedHistogramTest, CorruptSampleCounts);
 
   // In the case where this class manages the memory, here it is.
   std::vector<HistogramBase::AtomicCount> local_counts_;
 
   // These are raw pointers rather than objects for flexibility. The actual
   // memory is either managed by local_counts_ above or by an external object
   // and passed in directly.
   HistogramBase::AtomicCount* counts_;
   size_t counts_size_;
 
@@ skipping 28 matching lines @@
   const HistogramBase::AtomicCount* counts_;
   size_t counts_size_;
   const BucketRanges* bucket_ranges_;
 
   size_t index_;
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_SAMPLE_VECTOR_H_